This invention relates to an air chuck for use in a capping or uncapping machine. More particularly, the invention relates to an improvement in an air chuck which holds a screw cap of a bottle in a capping or uncapping machine.
The capping or uncapping machine is provided with a rotary device which receives bottles from a conveyor and moves the bottles on a circular locus and air chucks which are disposed right above the received bottles. The air chucks revolve while holding bottle caps from the receiving to the releasing of bottles by the rotary device, thereby screwing caps onto bottles or unscrewing caps from bottles.
The cap holding portion of the conventional air chuck is composed of a holding member which is fitted in a chuck casing and is made of a soft elastic material and a compression disk which presses and deforms the holding member under the action of compressed air. Thus, when a bottle cap is led into the central bore of the holding member, the holding member is deformed by the pressure of the compression disk, thereby seizing the cap.
In such a prior art air chuck, however, since the holding member must be deformed by the pressure of the compression disk, the holding member must be made of a sufficiently soft elastic material so as to seize reliably a cap. As a result, wearing and deterioration of holding member occurs and the long term use of the member cannot be expected.